1. Field of the Invention
This invention relates to a muffler for use during the production of multifilament, synthetic yarn. In particular, it relates to a muffler for use in conjunction with a plurality of aspirators, wherein the exhaust tubes of the aspirators are clustered for discharge by and through the muffler which reduces audible noise collectively emitted at the exit ends of the exhaust tubes by as much as 16 .DELTA. dB(A) and more.
Throughout the present specification and claims, the term "dB(A)" (decibels A-weighted) connotes the unit of measurement of sound level corrected to the A-weighted scale, as defined in ANSI S1.4-1971, using a reference level of 20 micropascals (2.times.10.sup.-5 Newtons per square meter). The term " .DELTA. dB(A)" refers to the difference between the two noise levels where each level is expressed in units of dB(A). The term "yarn" is employed in a general sense to indicate strand material, either textile or otherwise, and including a continuous, often plied, strand composed of fibers, filaments, glass, metal, asbestos, paper, or plastic, or a noncontinuous strand such as staple, and the like. An "end" is one or a contiguous group of such strands of yarn.
The invention is applicable to many phases of yarn handling, the particular use disclosed herein being merely illustrative and not limiting thereof.
2. Prior Art
Aspirators are frequently used in yarn producing processes for transporting yarn. For example, yarn ends thrown through an interfloor tube subsequent to extrusion and quenching may be picked up by an aspirator and carried off to waste until an operator can pick up the yarn end with a handheld aspirator or gun to continue string-up. Also, panel aspirators may be strategically located to aspirate off, when triggered, broken yarn ends to prevent the yarn from snarling or hanging up. Aspirators may also function as temporary collecting devices during the windup stage when starting new packages.
Noise is produced at and downstream of the point at which high velocity air is introduced into the aspirator passageway. The sound waves thus generated are then propagated through the aspirator inlet and outlet ends. U.S. Pat. No. 4,024,698 to Weiss et al., hereby incorporated by reference, teaches a muffler which reduces audible noise emitted at the inlet end of an aspirator by up to 22.5 .DELTA. dB(A). U.S. Pat. No. 4,030,651 to Weiss et al., hereby incorporated by reference, teaches an aspirator exhaust muffler which reduces audible noise emitted at the exit end of an interfloor tube by up to 33.5 .DELTA. dB(A).
The noise travelling through the outlet end of the aspirator passes, along with the aspirated yarn, through exhaust pipes or tubes to a collection point. Given the multiplicity of production positions, each with one or more associated aspirators, normally arranged in rows within a yarn producing plant, it is highly desirable for reasons of cost to have a muffler capable of reducing the noise emitted collectively by the exhaust tubes of the aspirators while simultaneously bringing all of the waste yarn transported thereby to a single collection point. The noise emitted, as measured approximately 6 inches (15.24 cms.) downstream of and on the center line of 16 clustered aspirator exhaust tubes, has been found to exceed 110-112 dB(A) in some instances without use of this invention. The frequency component of exhaust tube noise is situated in the high frequency levels, i.e., greater than 2,000 cycles per second, which has been shown to be more harmful than the low frequency levels.
U.S. Pat. No. 4,127,183 to McLarty is believed to be pertinent art.